For the US, in 2017, they updated " some of the calculations used to estimate fuel economy. The new calculations are based on test data from model year 2011–2016 vehicles. So, they better reflect today's vehicle fleet of more fuel-efficient vehicles and advanced technologies such as hybrids and turbocharged engines."

Since the 10th gen was new in 2017, perhaps now with 2 years of owner experiences, they've noticed that the car does not get as good of mileage as originally expected. Some of the original EPA ratings may have been based on lab testing, vs actual vehicle testing in actual road conditions.

2019 Touring Coupe CVT 30/37/33 w/235/40/18 tires, mechanically identical, same weight as the EX, only real difference is the much bigger/wider tires. I have been averaging 34-36 in general mixed driving, some limited highway only, indicated 43.5. Given, the car has only 1300 mi, but is lower overall than my 16 was at this point. I believe it is due to the increased drag, friction, adhesion of the larger tires. Can't think of any other reason, hopefully, when it gets warmer and its broken in, things will improve, but it is rated lower by 3 mpg highway. So far have used only Shell 87 which is Toptier.